Containment tarpaulins are used to cover the beds of trucks, rail cars, barges and the like when transporting loads subject to dispersal during transport, such as the transport of trash to a disposal area such as a land fill or trash plant, in order to prevent the load from flying from the vehicle and thereby contaminating the surrounding area. Containment is also of concern when the load is of value, or when dispersal of the load could cause injury, such as when gravel is transported. Fast moving vehicles such as trucks are especially prone to release of the transported material as a result of high velocity air currents generated by the moving vehicle. A tarpaulin to cover a load must be of a size sufficient both to fully overlie the load and provide peripheral area for the tie down. Truck trailers are generally about 16 meters long and 2.4 meters wide and thus containment fabric is made oversized for such a trailer, the fabric might be 17.4 meters long and 4 meters wide.
In addition to load containment, tarpaulin-type constructions are used for other protective purposes, and as wrappings and coverings.
The prior art teaches the use of canvas, a tightly woven fabric, usually in a plain weave construction, for tarpaulin use. The weave construction utilized makes the fabric relatively costly to manufacture. In addition, being formed of large diameter warp and filling yarns, canvas is stiff, heavy and therefore often difficult to manipulate and cover the load contained in the vehicle. Often, because of the weight, more than one individual is required to put the canvas in place and tie it down. In addition, canvas has low stretch and is easily punctured by sharp articles. And, because canvas has a low permeability, canvas tends to lift from the load due to the airfoil created by a mound of load and the passing air current developed by the velocity of the vehicle. The lift and inflation of the tarpaulin creates a larger cross-sectional area which creates additional drag and therefore increased fuel consumption for the vehicle.
To overcome the high weight of canvas, loosely woven nonstretch filament yarn plain weave containment fabrics have been used. Such fabrics may be coated with resins, such as phenolics or urea formaldehydes, in an attempt to give stability to the loosely woven structure. Formaldehyde, however, is a known carcinogen and such treatment can pollute the atmosphere. There is also concern regarding the use of such treated fabrics. While light in weight, these containment fabrics are stiff and therefore difficult to handle. The nonstretch filament yarns, especially after coating, are especially resistant to stretching. As a result the containment tarpaulin often cannot be fitted tightly against the load, allowing the load to shift against the fabric, subjecting it to cuts, tears and punctures. Being of a coarse mesh count, once the fabrics are damaged they cannot easily be patched or otherwise repaired.
It is accordingly a purpose of the present invention to provide a tarpaulin-type fabric which is of light weight and rugged design.
A further purpose of the present invention is to provide a tarpaulin-type fabric having the capability to conform to the shape of a load about which it is placed.
Still a further purpose of the present invention is to provide a tarpaulin-type fabric which exhibits stretch and which has sufficient air permeability to prevent the generation of lift forces.